Heat exchange apparatus



Oct. 9, 1945. N Q ARTSA# 2,386,188

HEAT EXCHANGE APPARATUS Filed March 4, 1942 4 Sheets-Sheet 1 llllll! ATTORNEY Oct' 9, 1945. N. c. ARTsAY HEAT EXCHANGE APPARATUS Filed March 4, 1942 4 Sheets-Sheet 2 'INVENTOR /V/(HOLAS C RT/IY A ORNEY Oct. 9, 1945. N. c. ARTsAY I HEAT EXCHANGE APPARATUS Filed March 4, 1942 4 Sheets-Sheet 3 INVENTOR ATTORNEYi OCf- 9, 1945- N. c ARTsAY HEAT EXCHANGE APPARATUS Filed March' 4, 1942 4 Sheets-Sheet 4 lNvENToR /V/c/fous C. APT A y BY ATTO R N Ev Patented Oct. 9, 1945 asse-,iss

HEAT EXCHANGE APPARATUS E .Nicholas o. Amay; vaincue, mr., miglior to' Foster Wheeler Corporation, New York, N. Y., a corporation of NewYork i Application Marchv 4, 1942, Serial No. 433.263

Claims. (Cl. 257-220) o This invention relates to heat exchange apparatus and more particularly `pertains to apparatus for heating air for use in vapor generators by heat recovered from the flue gases of said generators. y

In vapor generators using pulverized fuel, it is ldesirable not only to heat. the air used for supporting combustion in the fuel burners, commonly termed secondary air, but it is also desirable to heat the primary air which is used in drying the fuel'.` Generally, the degree to which the l horizontally spaced groups of vertically extendprimary air must beh'eated to properly dry the fuel is higher than the degree to which the secondary air maybe heated in recovering heat of the ilue gas.

The invention when applied to the generation of steam provides a heat exchanger in which primary and secondary air used in the steam generator is heated by heat recovered from the ue gases of the generator and in which the primary air maybe heated to a higher degree than the .secondary air. In the apparatus of this invention, the primary air temperatu e is controlled to provide at all boiler loa or ratings the degree lof heat required to dry the fuel, in

' accordance with the amount of moisture in the fuel. l

'I'he invention will be understood from the following description when considered in connection with the accompanying drawings forming a f part thereof andin which:

Fig. 1 is a-partial vertical sectional view of one form of steam generator embodying the invention:

I Fig. 2 is a somewhat enlarged partial vertical sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a horizontal sectional view taken on the line 3 3 of Fis. 2;

Fig. 4 is a horizontal sectional view taken on 'the line 4---4 of Fig. 2;

Fig. 5 is a vertical sectional view taken on line 5-5 of Fig. 2 Fig. 6 is a perspective view of the form of the invention illustrated in Figs. 1-5 of the drawings,

'and 4 Fig. ,7 is a vertical sectional view of another I form of the invention,

Like characters. of reference refer to like parts throughout the' severall views.

Referring to the drawings, reference numeral I0 designates the setting of a steam generator having an upper steam and water drum II connected to a lower drum I2 by a vertical bank of steam generating tubes I3 and an adjacent group of horizontally extending tubes I4. Also extending between the drum vI'I and the drum I2 rare ing tubes I5 having suitable flow directing bafiles I1`disposed between the groups.

A furnace chamben I8 lis positioned beneath the groups of tubes I3 and I4`. and the groups I5, so that the gases of combustion therefrom in passing outwardly thereof will pass over the tube groups. The chamber I8 is deilned by a vertical rear wall I3, a front wall 2li, a side wall 2I, an opposite side wall, not shown, and a roof 22 extending over the top of the chamber to the drum II. The walls of the furnace are water cooled,

the front wall 2li being lined by tubes 23 connected tothe drumy II' through headers 24 and tubes 25. The rear wall I3 is lined by water wallo tubes 23connected to the drum I2 while the side wall 2l is lined by tubes 21 connected to the drum Il through header 23 and tubes 29.

Pulverized fuel burners 30 are disposed in the front wall 23 ofthe furnace chamber and receive pulverized fuel through the conduits 3|- from a fuel pulverizing mill, not shown.` A superheaterA 32 is disposed between two of the groups of tubes i5 and is adapted to Areceive saturated steam from thedrum II through a conduit 34.

Gases of combustion from the furnace chamber I8 flow over the several tube groups and the superheater and pass upwardly over the vertical bank of tubes I3 and then downwardly over` an economizer 36 in ue passage 31, thereafter passing upwardly into an air heater through .the passage 38. The passage 38 is enlarged above a partition 33 between passages 31 and 38 to form an outlet passage 40, the front wall 4I of which is inclined over the roof 42 at substantially the same angle as the roof and is formed around and separated from `a. duct 43 which provides a passage 44 in communication with the passage 31.

An air heater, adapted to heat primary and secondary air for the steam generator, comprises a plurality of vertically disposed and spaced tubes V 5I expanded into a tube plate 5I), and is positioned above the outlet passage 40. Gases leaving the tube bank I3 ow directly to the air heater through a passage 44 which has its inlet connected with the upper end of passage 3l. 'I'he tubes 5I are expanded into `a tube plate 52 at their upper ends, and they are enclosed in a casing comprising a front wall 53, a rear wall 54., and opposite side walls 55 and 56. The Acasing is enlarged at the top thereof beneath the tube plate 52 to form an air inlet chamber 51 and is also enlarged adjacent the bottom thereof to form a cham-ber. The tube plate 50 forms the bottom of the chamber 58 and covers the outlet passage 40. Gases are thereby prevented from passing into the tube casing and caused to pass upwardly through the tubes 5|. Air to be heated is supplied to the chamber 51 through ducts 59 and passed downwardly over the tubes 5| to the chamber 58 d is thereby heated. A substantial portion of the heated air passes from the chamber 58 linto lthe secondary air ducts 60 which conduct the. air to hot air ports 6| adjacent burners 38 in the front wall -28 of. the furnace. The remainder of the air passes from the chamber 58 into a primary air heating chamber 62 formed around the tubes 63 in the central portion of the bank of tubes'5|. The tubes 63, as shown, are of larger diameter than the tubes 5| but may, if desired, be of the same size. The chamber 62 is formed by end partitions 64 and 65 which separate the chamber from the remainder of the interior of the casing, and by .the fr ont wall 53 and rear wall 54 of the casing. The end partitions extend below the tube plate 58 downwardly intol the passage 48. As shown-in Fig. 1, the front wall 53 has an extension 66 which projects upwardly and is fastened to the tube plate 52, and the rear `wa1l 54 has an extension 61 likewise projecting upwardlyA and is fastened to the plate 52 forming respectively front and rear walls for.

' the upper portion of the chamber 62. The front and rear walls respectively, have extensions 68 andy 69 which project downwardly to a point short of the tube plate 50 thereby providing front and rear walls for the lower portion of the chamber 62 and forming an inlet opening 18 into the chamber 62 in the rearwall thereof and a discharge opening t1| in the front wall of the chamber. The inlet opening 18 is in communication with the chamber 56 while the discharge opening 1| is in communication with a. primary'airydischarge chamber 12'formed within the chamber 58- by extensions 13 and 14 on the partitions 64 and 65 respectively which extensions extend between the top and bottom of the chamber andv separate the` discharge chamber 12 from the chamber 58. A primary air outlet duct 15 is connected to the chamber'12 and is adapted to conductNheated air therefrom to al pulverizer not shown.

A baiile 18 which extends vertically from the tube plate 50 to a point short of the' upper tube plate 52 is positioned in the primary air heating chamber 62 -between the partitions 64 and ,65

Vsubstantially intermediate the front and rear walls of the casing thereby dividing the chamber 62 into an inlet passage 16 in communication with the chamber 58 through the opening 18 and a discharge passage 11 in communication with the primary air discharge chamber 12 through the f opening 1|. The passages 16 and 11 communi- :cate with one another through the space above the bame 1s. y

The tubes 63 in the passage 11 are in communication through the inlet ends thereof with the passage 44 in the duct 43 through which thesel lin communication with a connecting chamber 19 formed by a cap 80 above the tube plate 52. The upper ends of the tubes 63 disposed in the passage 16- communicate with the connecting chamber 19 whence they receive'gases and discharge the same from their lowerfends into the l outlet passage 48. Discharge of the gases from the lower end of the tubes into thepassage 40 is controlled by dampers 8|.

` Gases of combustion after passing over the economi'zer 36 flow upwardly in the passage 38' and enter the voutlet passage 40 where they mix with gases passing through the dampers 8| from the primary air heating section. Gases from the outlet passage lllow upwardly in the tubes 5|` and pass from the upper ends thereof into the 1u stack 82.

In operation, gases of combustion from the furnace chamber vI8 after passing over the bank of tubes I3 iiow into the passage 31, ow over the economizer and through passages 38 and 40 to' the air heater. Part of the gases will flow through passage 44 in conduit 43 to therair heater, the quantity depending upon the position of the dampers 8|. The gases leaving outlet passage 48 flow into and through the secondary air heating tubes 5| and enter the stack 82. Gases ilowing through the passage 44 in duct 43, enter the tubes 63 in the passage 11 of the primaryair heating chamber Y62 and pass upwardly into the connecting chamber 19. From the 4connecting `chamber 19, the gases pass downwardly through passage owing upwardly from the chamber 44. yf'lhe gases flowing through the tubes 63. since they are passed directly into theI tubes, are hotter than the gases owing through ,the tubes' 5| which gases are rstpassed over the economizer 36.

Air to be heated enters the chamber 51 through the ducts 59, passes downwardly through the bank of tubes 5| and enters the chamber 58.- The greater part of the air thus heated, which constitutes the secondary air, flows from the chamber 56 through the ducts 68 to the hot air ports ,6|

' in the front wall 28; of the furnace chamber. o The remainder of .thel air from the chamber 58 passes through the inlet opening 18 into the passage 16 in the primary air heating chamber 62 and flows upwardly over thel/tubes 63 in the passage. From the chamber 16, the air passes over the discharge opening 1I into the primary air discharge chamber 12 thereafter entering the primary airoutlet duct 15 through which it is lpassed to thefuel pulverizer.

The degree to which the air passing through the primary air heating chamber is heated, is regulatedmby the dampers 8| which control the amount of gases passed through the primary air heating'tubes ,63 from the duct 48 and the chamber 43. The gases from the tubes 63` in the pri-` mary air heating chamber, after passing through the dampers, enter the passage where they are mixed with gases from the passage 38 thereby increasing the temperature of the gases passed from the secondary air heating tubes 5| which,

particularly when the steam generator is being 65 operated at low loads, -prevents the gases in the secondary air heating section from reaching theY dew point and thereby causing damage to the section by corrosion. i

The operation of theform of the invention shown in Fig. rI is substantially the same as in the form shown in Fig. 1 with the exception, however, that in the form shown in Fig. 1 the primary air is heated in the secondary heating section, whereas in the apparatus of Fig. 7` the primary air is passed directly to the primary air the tubes 63 in the passage 16 and into the pas# sage 48 becoming mixed with the gases in said the top of the balile 18 into the passage 11 then The air thus heated in the primary air heatingchamber 62 flows from the passage 11 through f assensoA heating section without being preheated in the l tensions 85 and 88 respectively which extend upwardly to a point short of the tube plate 52 thereby forming an intake opening 81 and a discharge opening 88 in the primary air heating chamber. A primary air discharge chamber 88 separated from the chamber 51 by an extension on end partitions 64 and 65 is in communication with the discharge opening 88 and the primary air outlet duct 15. Air to be heated passes from the duct 59 into the chamber 51 whence a portion of it passes directly into the passage 11 of the primary air heating chamber through the opening the 'first air heater and the path of flow of the f gases, said means being in communication with I heater, conduit means' in communication with the opposite end of said some of the tubes of the path of iiow of the gases at a point in ad- Vance of the heat absorbing device in respect 81 downwardly through the passage 11 around the end of the baiiie, upwardly in the passage 16,

vthrough the discharge opening 88 into the chamber 89 and thence into the conduit 15S) The re-. mainder of the air passes from the chamber 51 downwardly over the tubes -5| and into the chamber 58 whence it enters the conduits 60.

Although the invention has been disclosed as embodied in a steam generator adapted for the combustion of low volatile fuels in which an air heater is employed to preheat primary air and secondary air, the invention is applicable to any form of vapor generator in which an economizer or other heat recovery device and an air heater are employed to recover heat from the ue gases. It is understood that changes may be made in the location and relative arrangement of the parts of the apparatus shown and described herein, lwithout departing from the principles of the invention, which is not to be limited excepting by the scope of the appended claims.

What is claimed is;

1. Heat exchange apparatus for extracting heat from gases comprising a heatV absorbing' device positioned in the path of flow of a Iportion only of said gases, air heating apparatus comprising a first air heater and a second air heater through each of which air and gases ow in indirect heat exchange relationship, means for introducing air into said air heaters, each air heater having a gas inlet and a gas outlet, the rst air heater having its gas inlet in communication with Ithe path of flow of the gases at a point therein in advance of said heat absorbing device, imeans to the direction of flow of the gases, means through which the gases from the opposite end 'of said other of the tubes of the rst air heater flow tothe tubes of the second air.heater. means for introducing air into said air heater to pass in heat exchange relationship with the tubes, means through which gases pass from the second air heater, and means through which heated air is conducted from the air-heaters.

3. Heat exchange apparatus for extracting heat from gasescomprising a heat absorbing device positioned in the path of flow of a portion only of said gases, air heating apparatus comprising a first air heater and a second airheater, a plurality of spaced tubes in each heater, the tubes of the second air heater being in communication with the path of new of the gases at a point beyond the heat absorbing device in respect to the direction of ow of gases, some of the tubes .of the first air heater being in communication with other of the tubes thereof at one end of said heater, conduit means in communication with the opposite end of said some of the tubes of the rst air heater andthe path of flow oi the gases, said means being in communication with the path of ow of the gases at a point in advance of the heat absorbing device inrespect tothe direction tion, other air heating sections at opposite. sides through which gases from the outlet of the rst air heater flow to the second air heater, the second air heater having its gas inlet in communica` tion with said path at a point therein beyond4 said heat absorbing device, means through which gases pass from the second air heater, and means through which heated air is conducted from the air heaters. v

2. Heat exchange apparatus for extracting heat from gases comprising a heat absorbingI device positioned in the path of flow of a. portion only of said gases, air heating apparatus comprising a first air heater and a second air heater. a

plurality of spaced tubes in each heater, the tubes of flow of the gases, means through which gases from the opposite end of said other of-the tubes of the first air heater ilow to the tubes of the second air heater, means for introducing air into the second air heater to pass in heat exchange relationship with the tubes therein, the 'second air heater ,being connected with the iirst air heater so -that a portion of the air pret-heated in the second heater flows into the first heater, means through which gases pass `from the second air heater, and means through 4which heated air is conducted from the air` heaters.

vdi. Heat exchange apparatus for extracting heat fromv gases comprising, a heat absorbing device positioned in the path of flow ofa portion only of said gases, air heating apparatus comprising a substantially centrally disposed air heating secof said centrally disposed section and separated therefrom, the air heating sections ,being laterally arranged at substantially the same elevation, -a plurality oi?` spaced tubes in said sections, the tubes of said other air heating sections being in communication with the path of flow of the gases at a point beyond the heat absorbing device in respect to the direction of now of gases, the tubes of the centrally disposed air heating sec-- tion being in communication with each other at one end, conduit means in. communication with the opposite end of `some of the tubes of the centrally disposed air. heating section and the path of flow of the gases, said means being in communication with the path of flow of the gases at a point in advanceof the heat absorbing device in respect to the direction of ilow of the gases, means through which gases from the ofthe second air heater being in communication with the path of fiow of the'gases at a point beyond the heat absorbing device in respect to the direction of flow of gases, some of the tubes of the first-air heater being in communication with other of thetubes thereof at one end of said opposite end of other of the tubes of the centrally disposed air heating section'iow to the tubes of said other air heating sections, means for introducing air into the air heating sections to pass -in heat exchange relationship with the tubes,

5 means through which the gases pass from the communication with the path of ow of the gases at a point beyond the heat absorbingfdevice in respect to the direction of flow of gases, the tubes of the centrally disposed air heating sectionfbe ing in communication with each other at one end, conduit means in communication with the opposite end of some of the tubes of the centrally luieren-heating sections, and means throughL .which heated airis conducted from the air pre-heated air therefrom, conduits for conducting gases to each air heater, the ,conduit for the centrally disposedsection being constructed and arranged to conduct gases to a part only of one end of said central section, means at the other end of the central section to cause gases discharged from said part to flow into and through another part oi' the central section in a direction opposite to the ow through said part, means to conduct gases discharged from said other part of the central section lto the inlet ends of said other air heating sections for how therethrough, means for controlling the tlow of gases through the centrally disposedl section. means through which gases ow from saidj other sections, and means through which-heated air is conducted lfrom the centrally disposed section and said other` sections.

8. Air heating apparatus having a substantially centrally disposed air heating section, other air heatingsections at opposite sides of the centrally disposed air heating section and the path of iiow of the gases, said means being in communication with the path of flow of the gases at a point in advance of theheat absorbing device in respect to the direction of ow of the gases, means through which gases from the opposite end of other of the tubes of the centrally disposed air heating section flow to the tubes of said other air` heating sections, means for introducing air into said other air heating sections, the other airv heaters being connected with the centrally disposed heater so thata portion of the air preheated in the other air heating sections ows into said centrally disposedheater, meansthrough -which the gases pass from the other air heating sections, and means through which heated air is A conducted from the air heaters.

6. Air heating apparatus through which gases ow in heat exchange relationship with air, said apparatus having a substantially centrally disposed air heating section, other air heating sections at opposite sides of said centrally disposed section and separated therefrom, the air heating sections being laterally arranged at substantially the same elevationymeans for introducing air into said air heating sections, conduits .for conducting gases to each air heater, the conduit for means to conduct gases discharged from said other part of the central section to the inlet ends of saidother air heating sections for flow there-' through, means for controlling the iiow of gases through the -centrally disposed section, means through which gases iiow from said othertions, and means `througln which heated an conducted from the centrallyr disposed sect1 and vsaid other sections.

7. Air heating apparatus through which gases iiow in heat exchange relationship with air, said apparatus `having asubstantially centrally distions at opposite sides of said centrally disposed section and separated therefrom, the air heating sections being laterally arranged at substantially the same elevation, means or introducing air -to be heated into said other heating sections. the centrally disposed heating section being in posed air' heating section, other,airfheating secdisposed section and separated therefrom, the other air heating sections being laterally ar ranged at substantially the same elevation, a

.plurality of spaced tubes in said sections, conduits for conducting gases to the tubes of each air heater, the conduit for the centrally disposed section being constructed and arranged to conduct gases to one end of some only o the tubes of said central section,` means at the other end of thetubes of the central section to cause gases discharged from said some tubes to iiow into and through others of the tubes of the central section in a direction opposite to the flow through said slime tubes, means to conduct gases discharged from said other tubes of the central section to the inlet ends of said other air heating sections for flow therethrough, means for introducing air into the heating sections to pass in heat exchange relationship with the tubes, control means for controlling the ow of gases through the centrally disposed section, means through which gases pass vfrom said other sections, and means through which heated air is conducted from the air heaters.

. 9. Heat exchange apparatus for recovering waste heat from gases comprising an air heating device having a plurality of air heaters through each of which air and gases ilow in indirect heat exchange-relationship, each air heater having separate air and gas inlets andseparate air and gas outlets, a heat absorbing device, means for conducting waste gases to the heat absorbing device for flow thereover, means for conducting gases discharged from said device to at least one but not all of the air heaters, a by-pass conduit in' communication with the .means conducting waste gases to the heat absorbing device for conducting some of the waste gases to another air heater without flowing over the heat absorbing device, and means for conducting gases discharged from' said other airheater to the inlet ends of said at least one air heater, the construc-,.

^ tion and arrangement being such that gases entering the airheatersare at different temperatures andthe air owing through said heaters is heated to diii'grent temperatures, and gases from the gas outlet of the heater in which air is heated to` a higher temperature mixes with the gases which ilow'through another heater in which .theai'r is heated-,fito a lower temperature.,

'10." Heat exchange apparatus for recovering -wastev heat from gases comprising an air heatingl device havinga plurality of air heaters through communication with said other sections to receive .each of which air andgases ow in indirect heat exchange relationship, each air heater having separate air and gas inlets and separate airl and gas outlets,a heat absorbing' device, means for conducting waste gases to' the heat absorbing device for flow thereover, means for conducting,

gases discharged from said device to at least one but not all of the air heaters, a by-pass conduit l in communication with the means conducting waste gases to the heat absorbing device for conducting some of the waste gases to another air ln heater without nowing over the heat absorbing device, means for conducting gases discharged from said other air heater to the inlet ends of said at least one air heater,` the construction and arrangement-being such that gases entering the air heaters are at different temperatures and the air flowing through said heaters isheated to diierent temperatures, and gases from the gas outlet, of the heater in which air isheated to a higher NICHOLAS C. `ARTSAY. 

